Year-end Sale % OFF 
Abstract
Heat pump water heaters are highly efficient hot water supply systems that effectively utilize the heat of outdoor air via heat pump technology. Many studies have been conducted to optimize the design and operation of heat pump water heaters from the perspective of climate change mitigation. Air-source heat pump water heaters, which absorb heat from the outdoor air and emit cold exhaust, can also be expected to alleviate the urban heat island effect; however, this has not been studied extensively. To estimate the impact of cold exhaust on building-scale climate, we conducted a multipoint measurement of the outdoor thermal environment around a low-rise apartment building equipped with air-source heat pump water heaters, in both summer and winter. Observations showed a substantial cooling effect that decreased air temperatures by 1 °C within the site boundary on summer nights when multiple heat pump water heaters operated concurrently. The analysis revealed that the sensitivity of the ambient temperatures to cold exhaust depends strongly on local atmospheric conditions. The most influential factor was the wind direction: the sensitivity increased significantly when the exhaust outlet location was at the lee side of the building. Naturally, the wind speed also affected the sensitivity, which tended to be higher when the wind speed was lower. The convective stability near the ground surface, however, showed no significant influence over the sensitivity.
Highlights
According to IPCC AR4 WG2 (2007), it is clear that mitigation alone cannot prevent the effects of climate change
Around a low-rise apartment building in which all apartments have air-source heat pump water heaters (ASHPWHs) installed, we observed the thermal environment in building scale during summer and winter
The following findings concerning the cooling effect of cold exhaust on ambient outdoor temperature are provided as: (1) The greatest reduction in 1.5 m air temperature exceeded 1 °C and it was shown to be concentrated on the side where the exhaust outlets of ASHPWH were placed
Summary
According to IPCC AR4 WG2 (2007), it is clear that mitigation alone cannot prevent the effects of climate change. Urban areas, which consume a large amount of energy, suffer from the combined impact of global warming and the urban heat island (UHI) effect. Water heating accounts for a large percentage of total energy consumption in the domestic sector, estimated at 14% in the USA (IEA 2018), 16.8% in the UK (BEIS 2019), and 29.1% in Japan (ANRE 2019); it is a major source of CO2 emissions. The air-source heat pump water heater (ASHPWH) system is a highly efficient hot water supply device that employs heat pump technology to effectively utilize the heat of outdoor air. This is a technology expected to contribute to the mitigation of climate change by reducing CO2 emissions
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
